Large variations in resource utilization have been reported for diagnosis-related-groups (DRGs) in general and substance abuse including alcohol) related DRGs in particular. It is suspected that this could be an important contributing factor prolonging length-of-stay for patients that have substance abuse and/or alcoholism as a comorbid condition in their records. To test this hypothesis, the proposed study will analyze the effect of substance abuse (including alcoholism) on the severity of patient care at the Harborview Medical Center. DRGs that have substance abuse and/or alcoholism mentioned as a comorbid condition will be compared for length-of-stay and charges, to similar DRGs that have other comorbid conditions mentioned in the discharge records. This study will help in developing an index for adjustment of payments for DRGs that frequently have substance abuse as a comorbid condition. Since public hospitals receive a disproportionate share of patients abusing alcohol and/or drugs, this adjustment will lead to a greater predictability and homogeneity of the DRG system. Our preliminary analysis indicates that substance abuse and alcoholism as a comorbidity is associated with longer than average LOS and charges at Harborview Medical Center.